Tumor evasion of the immune system: inhibiting p38 MAPK signaling restores the function of dendritic cells in multiple myeloma

Immune-Pathogenesis of Myeloma

This research indicates that monoclonal gammopathy of undetermined significance (MGUS) and myeloma may stem from chronic immune activation and inflammation, causing immune dysfunction and spatial immune exclusion. As the conditions progress, a shift toward myeloma involves ongoing immune impairment, affecting both innate and adaptive immunity. Intriguingly, even in advanced myeloma stages, susceptibility to immune effector cells persists. This insight highlights the intricate interplay between immune responses and the development of these conditions, paving the way for potential therapeutic interventions targeting immune modulation in the management of MGUS and myeloma.

The immune system in multiple myeloma and precursor states: Lessons and implications for immunotherapy and interception

Multiple myeloma (MM) and its precursor monoclonal gammopathy of undetermined significance (MGUS) are distinct disorders that likely originate in the setting of chronic immune activation. Evolution of these lesions is impacted by cross-talk with both innate and adaptive immune systems of the host. Harnessing the immune system may, therefore, be an attractive strategy to prevent clinical malignancy. While clinical MM is characterized by both regional and systemic immune suppression and paresis, immune-based approaches, particularly redirecting T cells have shown remarkable efficacy in MM patients. Optimal application and sequencing of these new immune therapies and their integration into clinical MM management may depend on the underlying immune status, in turn impacted by host, tumor, and environmental features. Immune therapies carry the potential to achieve durable unmaintained responses and cures in MM.

The mechanisms on evasion of anti-tumor immune responses in gastric cancer

The immune system and the tumor have been at each other's throats for so long that the neoplasm has learned to avoid detection and avoid being attacked, which is called immune evasion. Malignant tumors, such as gastric cancer (GC), share the ability to evade the body's immune system as a defining feature. Immune evasion includes alterations to tumor-associated antigens (TAAs), antigen presentation mechanisms (APMs), and the tumor microenvironment (TME). While TAA and APM are simpler in nature, they both involve mutations or epigenetic regulation of genes. The TME is comprised of numerous cell types, cytokines, chemokines and extracellular matrix, any one of which might be altered to have an effect on the surrounding ecosystem. The NF-kB, MAPK, PI3K/AKT, JAK/STAT, Wnt/β-catenin, Notch, Hippo and TGF-β/Smad signaling pathways are all associated with gastric cancer tumor immune evasion. In this review, we will delineate the functions of these pathways in immune evasion.

Deciphering mechanisms of immune escape to inform immunotherapeutic strategies in multiple myeloma

Multiple myeloma is an incurable cancer characterized by the uncontrolled growth of malignant plasma cells nurtured within a permissive bone marrow microenvironment. While patients mount numerous adaptive immune responses directed against their disease, emerging data demonstrate that tumor intrinsic and extrinsic mechanisms allow myeloma cells to subvert host immunosurveillance and resist current therapeutic strategies. Myeloma downregulates antigens recognized by cellular immunity and modulates the bone marrow microenvironment to promote uncontrolled tumor proliferation, apoptotic resistance, and further hamper anti-tumor immunity. Additional resistance often develops after an initial clinical response to small molecules, immune-targeting antibodies, immune checkpoint blockade or cellular immunotherapy. Profound quantitative and qualitative dysfunction of numerous immune effector cell types that confer anti-myeloma immunity further supports myelomagenesis, disease progression and the emergence of drug resistance. Identification of tumor intrinsic and extrinsic resistance mechanisms may direct the design of rationally-designed drug combinations that prevent or overcome drug resistance to improve patient survival. Here, we summarize various mechanisms of immune escape as a means to inform novel strategies that may restore and improve host anti-myeloma immunity.

Dendritic Cell-Based Immunotherapy in Multiple Myeloma: Challenges, Opportunities, and Future Directions

Immunotherapeutic approaches, including adoptive cell therapy, revolutionized treatment in multiple myeloma (MM). As dendritic cells (DCs) are professional antigen-presenting cells and key initiators of tumor-specific immune responses, DC-based immunotherapy represents an attractive therapeutic approach in cancer. The past years, various DC-based approaches, using particularly ex-vivo-generated monocyte-derived DCs, have been tested in preclinical and clinical MM studies. However, long-term and durable responses in MM patients were limited, potentially attributed to the source of monocyte-derived DCs and the immunosuppressive bone marrow microenvironment. In this review, we briefly summarize the DC development in the bone marrow niche and the phenotypical and functional characteristics of the major DC subsets. We address the known DC deficiencies in MM and give an overview of the DC-based vaccination protocols that were tested in MM patients. Lastly, we also provide strategies to improve the efficacy of DC vaccines using new, improved DC-based approaches and combination therapies for MM patients.

The Association Between Gut Microbiota, Toll-Like Receptors, and Colorectal Cancer

The large number of microbes found in the gut are involved in various critical biological processes in the human body and have dynamic and complex interactions with the immune system. Disruptions in the host’s gut microbiota and the metabolites produced during fermentation promote the development of intestinal inflammation and colorectal cancer (CRC). Toll-like receptors (TLRs) recognize specific microbial-associated molecular patterns specific to microorganisms whose signaling is involved in maintaining intestinal homeostasis or, under certain conditions, mediating dysbiosis-associated intestinal inflammation. The signaling pathways of TLRs are described first, followed by a discussion of the interrelationship between gut microbes and TLRs, including the activation of TLRs by gut microbes and the effect of TLRs on the distribution of gut microbiota, particularly the role of microbes in colorectal carcinogenesis via TLRs. Finally, we discuss the potential roles of various TLRs in colorectal cancer.

Laboratory Mice - A Driving Force in Immunopathology and Immunotherapy Studies of Human Multiple Myeloma

Mouse models of human cancer provide an important research tool for elucidating the natural history of neoplastic growth and developing new treatment and prevention approaches. This is particularly true for multiple myeloma (MM), a common and largely incurable neoplasm of post-germinal center, immunoglobulin-producing B lymphocytes, called plasma cells, that reside in the hematopoietic bone marrow (BM) and cause osteolytic lesions and kidney failure among other forms of end-organ damage. The most widely used mouse models used to aid drug and immunotherapy development rely on in vivo propagation of human myeloma cells in immunodeficient hosts (xenografting) or myeloma-like mouse plasma cells in immunocompetent hosts (autografting). Both strategies have made and continue to make valuable contributions to preclinical myeloma, including immune research, yet are ill-suited for studies on tumor development (oncogenesis). Genetically engineered mouse models (GEMMs), such as the widely known Vκ*MYC, may overcome this shortcoming because plasma cell tumors (PCTs) develop de novo (spontaneously) in a highly predictable fashion and accurately recapitulate many hallmarks of human myeloma. Moreover, PCTs arise in an intact organism able to mount a complete innate and adaptive immune response and tumor development reproduces the natural course of human myelomagenesis, beginning with monoclonal gammopathy of undetermined significance (MGUS), progressing to smoldering myeloma (SMM), and eventually transitioning to frank neoplasia. Here we review the utility of transplantation-based and transgenic mouse models of human MM for research on immunopathology and -therapy of plasma cell malignancies, discuss strengths and weaknesses of different experimental approaches, and outline opportunities for closing knowledge gaps, improving the outcome of patients with myeloma, and working towards a cure.

Centrosome Dynamics and Its Role in Inflammatory Response and Metastatic Process

Metastasis is a process by which cancer cells escape from the location of the primary tumor invading normal tissues at distant organs. Chromosomal instability (CIN) is a hallmark of human cancer, associated with metastasis and therapeutic resistance. The centrosome plays a major role in organizing the microtubule cytoskeleton in animal cells regulating cellular architecture and cell division. Loss of centrosome integrity activates the p38-p53-p21 pathway, which results in cell-cycle arrest or senescence and acts as a cell-cycle checkpoint pathway. Structural and numerical centrosome abnormalities can lead to aneuploidy and CIN. New findings derived from studies on cancer and rare genetic disorders suggest that centrosome dysfunction alters the cellular microenvironment through Rho GTPases, p38, and JNK (c-Jun N-terminal Kinase)-dependent signaling in a way that is favorable for pro-invasive secretory phenotypes and aneuploidy tolerance. We here review recent data on how centrosomes act as complex molecular platforms for Rho GTPases and p38 MAPK (Mitogen activated kinase) signaling at the crossroads of CIN, cytoskeleton remodeling, and immune evasion via both cell-autonomous and non-autonomous mechanisms.

Genetically engineered myeloid cells rebalance the core immune suppression program in metastasis

Metastasis is the leading cause of cancer-related deaths, and greater knowledge of the metastatic microenvironment is necessary to effectively target this process. Microenvironmental changes occur at distant sites prior to clinically detectable metastatic disease; however, the key niche regulatory signals during metastatic progression remain poorly characterized. Here, we identify a core immune suppression gene signature in pre-metastatic niche formation that is expressed predominantly by myeloid cells. We target this immune suppression program by utilizing genetically engineered myeloid cells (GEMys) to deliver IL-12 to modulate the metastatic microenvironment. Our data demonstrate that IL12-GEMy treatment reverses immune suppression in the pre-metastatic niche by activating antigen presentation and T cell activation, resulting in reduced metastatic and primary tumor burden and improved survival of tumor-bearing mice. We demonstrate that IL12-GEMys can functionally modulate the core program of immune suppression in the pre-metastatic niche to successfully rebalance the dysregulated metastatic microenvironment in cancer.

Tumor-mediated inhibition of human dendritic cell differentiation and function is consistently counteracted by combined p38 MAPK and STAT3 inhibition

Targeting dendritic cells (DC) through the release of suppressive factors is an effective means for tumors to escape immune control. We assessed the involvement of downstream signaling through the JAK2/STAT3 and p38 MAPK pathways in tumor-induced suppression of human DC development. Whereas the JAK2/STAT3 pathway has been pinpointed in mouse studies as a key regulator of myeloid suppression, in human DC this is less well established. We studied the effects of STAT3 inhibition on the suppression of monocyte-derived DC differentiation mediated by a short-list of four predominant suppressive factors and found that pharmacological STAT3 inhibition could only counteract the effects of IL-6. Accordingly, in testing a panel of supernatants derived from 11 cell lines representing various types of solid tumors, STAT3 inhibition only modestly affected the suppressive effects of a minority of supernatants. Importantly, combined interference in the STAT3 and p38 pathways completely prevented inhibition of DC differentiation by all tested supernatants and effected superior DC function, evidenced by increased allogeneic T cell reactivity with elevated IL-12p70/IL-10 ratios and Th1 skewing. Combined STAT3 and p38 inhibition also afforded superior protection against the suppressive effects of primary glioma and melanoma supernatants and induced a shift from CD14⁺ cells to CD1a⁺ cells in metastatic melanoma single-cell suspensions, indicating a potential for improved DC differentiation in the tumor microenvironment. We conclude that combined interference in the STAT3 and p38 MAPK signaling pathways is a promising approach to overcome tumor-induced inhibitory signaling in DC precursors and will likely support clinical immunotherapeutic strategies.

MicroRNAs in the Tumor Microenvironment

The tumor microenvironment (TME) is decisive for the eradication or survival of any tumor mass. Moreover, it plays a pivotal role for metastasis and for providing the metastatic niche. The TME offers special physiological conditions and is composed of, for example, surrounding blood vessels, the extracellular matrix (ECM), diverse signaling molecules, exosomes and several cell types including, but not being limited to, infiltrated immune cells, cancer-associated endothelial cells (CAEs), and cancer-associated fibroblasts (CAFs). These cells can additionally and significantly contribute to tumor and metastasis progression, especially also by acting via their own deregulated micro (mi) RNA expression or activity. Thus, miRNAs are essential players in the crosstalk between cancer cells and the TME. MiRNAs are small non-coding (nc) RNAs that typically inhibit translation and stability of messenger (m) RNAs, thus being able to regulate several cell functions including proliferation, migration, differentiation, survival, invasion, and several steps of the metastatic cascade. The dynamic interplay between miRNAs in different cell types or organelles such as exosomes, ECM macromolecules, and the TME plays critical roles in many aspects of cancer development. This chapter aims to give an overview on the multiple contributions of miRNAs as players within the TME, to summarize the role of miRNAs in the crosstalk between different cell populations found within the TME, and to illustrate how they act on tumorigenesis and the behavior of cells in the TME context. Lastly, the potential clinical utility of miRNAs for cancer therapy is discussed.

Huaier Extractum Promotes Dendritic Cells Maturation and Favors them to Induce Th1 Immune Response: One of the Mechanisms Underlying Its Anti-Tumor Activity

Huaier, a sandy beige mushroom with anti-tumor effects, has been applied into Traditional Chinese Medicine for more than 1600 years. Previous studies showed that Huaier exerted its anti-tumor effects not only by direct action on tumor cells, but also indirectly by modulation of immune function. In the present study, we found that Huaier treatment significantly repressed tumor growth in mice with 4T1 breast cancer and resulted in significant accumulation of CD4⁺ T cells and mature dendritic cells (DCs) in the tumor microenvironment. In vitro experiments demonstrated that Huaier treatment promoted both DC2.4 and bone marrow derived DCs (BMDCs) to express costimulatory molecules, enhance production of IL-1β and IL-12p70, while it inhibited their phagocytic activities, suggesting that Huaier treatment promotes maturation of DCs. Furthermore, we found Huaier-treated DCs profoundly stimulated proliferation of alloreactive CD4⁺ T cells and drove them to differentiate into Th1 subset. Expression of PI3K, Akt, p-Akt, JNK, and p-JNK was up-regulated, while p-p38 MAPK was down-regulated in Huaier-treated BMDCs, suggesting that Huaier promotes maturation of DCs with potent ability to activate Th1 immune response via modulation of MAPK and PI3K/Akt signaling pathways. Our findings provide further evidence for the mechanisms underlying the anti-tumor activity of Huaier.

The non-linearity of RAF-MEK signaling in dendritic cells

Kinases form the major part of the druggable genome and their selective inhibition in human cancers has had reasonable clinical success. In contrast to tumorigenesis, the role of kinases in mediating immune responses is poorly understood. However, synergistic therapeutic regimens combining targeted therapy and immune therapy have been found to increase the median survival of tumor patients. In this context, we uncovered that RAF and MEK1/2 kinases, which are the integral parts of the classical MAPK cascade, have unique roles in driving DC differentiation and activation. RAF kinases are stabilized in their protein levels during DC differentiation and are obligatory for normal functioning of DCs. But, the targeting of MEK1/2 kinases with specific inhibitors did not phenocopy the effects observed with RAF inhibitors suggesting that RAF and MEK1/2 kinases may have specific and unique roles in driving immune responses, which deserves further studies to successfully administer these inhibitors in clinics.

MicroRNA-155 Suppresses the Translation of p38 and Impairs the Functioning of Dendritic Cells in Endometrial Cancer Mice

Background

Dendritic cells (DCs) are reported to play an important role in activating the anti-tumor immune responses. p38 MAPK14 signaling plays an important role in controlling their activity. Here, we identified that miR-155 suppressed the translation of p38 and impaired the functioning of dendritic cells in endometrial cancer.

Methods

HEC1A endometrial cancer cell lines were used for the study which was transfected in the C57BL/6 mice. Murine bone marrow-derived dendritic cells (BMDCs) were isolated from the mice. Target prediction was done by TargetScan which was confirmed by RT-PCR analysis. The protein expression was carried by Western blot analysis. Levels of IL-12 were evaluated by ELISA. Mice injected with HEC1A cells were subjected to tumor challenge study.

Results

On screening the binding sites of p38 MAPK14 gene, miR-155 was found to bind the 3ʹUTR directly and blocked its translation. The levels of miR-155 were upregulated in dendritic cells and RAW264.7 cells, miR-155 showed inhibitory effect on expression levels of p38. In dendritic cells, miR-155 was found to regulate the expression of IL-12, also miR-155 inhibitor stimulated the differentiation of Th1 cells in mice induced with endometrial cancer. In dendritic cells, miR-155 inhibited the expression of p38 gene and decreased their ability to interfere in tumor growth.

Conclusion

The study concludes suppressive role of miR-155 in the process of dendritic cells mediated anti-tumor immunity, also inhibiting miR-155 provides a novel strategy for countering endometrial cancer.

Oncolytic adenovirus ORCA-010 increases the type 1 T cell stimulatory capacity of melanoma-conditioned dendritic cells

Immune checkpoint blockade has resulted in durable responses in patients with metastatic melanoma, but only in a fraction of treated patients. For immune checkpoint inhibitors (ICI) to be effective, sufficient infiltration with tumor‐reactive T cells is essential. Oncolytic viruses (OV) selectively replicate in and lyse tumor cells and so induce an immunogenic form of cell death, providing at once a source of tumor‐associated (neo)antigens and of danger signals that together induce effective T cell immunity and tumor infiltration. Melanoma‐associated suppression of dendritic cell (DC) differentiation effectively hampers OV‐ or immune checkpoint inhibitor (ICI)‐induced anti‐tumor immunity, due to a consequent inability to prime and attract anti‐tumor effector T cells. Here, we set out to study the effect of ORCA‐010, a clinical stage oncolytic adenovirus, on DC differentiation and functionality in the context of human melanoma. In melanoma and monocyte co‐cultures, employing a panel of five melanoma cell lines with varying origins and oncogenic mutation status, we observed clear suppression of DC development with apparent skewing of monocyte differentiation to a more M2‐macrophage‐like state. We established the ability of ORCA‐010 to productively infect and lyse the melanoma cells. Moreover, although ORCA‐010 was unable to restore DC differentiation, it induced activation and an increased co‐stimulatory capacity of monocyte‐derived antigen‐presenting cells. Their subsequent ability to prime effector T cells with a type I cytokine profile was significantly increased in an allogeneic mixed leukocyte reaction. Our findings suggest that ORCA‐010 is a valuable immunotherapeutic agent for melanoma.

Myeloma escape after stem cell transplantation is a consequence of T-cell exhaustion and is prevented by TIGIT blockade

Autologous stem cell transplantation (SCT) remains a standard of care for multiple myeloma (MM) patients and prolongs progression-free survival. A small cohort of patients achieve long-term control of disease, but the majority of patients ultimately relapse, and the mechanisms permitting disease progression remain unclear. In this study, we used a preclinical model of autologous SCT for myeloma where the disease either progressed (MM relapsed) or was controlled. In the bone marrow (BM), inhibitory receptor expression on CD8⁺ T cells correlated strongly with myeloma progression after transplant. In conjunction, the costimulatory/adhesion receptor CD226 (DNAM-1) was markedly downregulated. Interestingly, DNAM-1^- CD8⁺ T cells in MM-relapsed mice had an exhausted phenotype, characterized by upregulation of multiple inhibitory receptors, including T-cell immunoglobulin and ITIM domains (TIGIT) and programmed cell death protein 1 (PD-1) with decreased T-bet and increased eomesodermin expression. Immune checkpoint blockade using monoclonal antibodies against PD-1 or TIGIT significantly prolonged myeloma control after SCT. Furthermore, CD8⁺ T cells from MM-relapsed mice exhibited high interleukin-10 (IL-10) secretion that was associated with increased TIGIT and PD-1 expression. However, while donor-derived IL-10 inhibited myeloma control post-SCT, this was independent of IL-10 secretion by or signaling to T cells. Instead, the donor myeloid compartment, including colony-stimulating factor 1 receptor-dependent macrophages and an IL-10-secreting dendritic cell population in the BM, promoted myeloma progression. Our findings highlight PD-1 or TIGIT blockade in conjunction with SCT as a potent combination therapy in the treatment of myeloma.

Dendritic cells as cancer therapeutics

The ability of immune therapies to control cancer has recently generated intense interest. This therapeutic outcome is reliant on T cell recognition of tumour cells. The natural function of dendritic cells (DC) is to generate adaptive responses, by presenting antigen to T cells, hence they are a logical target to generate specific anti-tumour immunity. Our understanding of the biology of DC is expanding, and they are now known to be a family of related subsets with variable features and function. Most clinical experience to date with DC vaccination has been using monocyte-derived DC vaccines. There is now growing experience with alternative blood-derived DC derived vaccines, as well as with multiple forms of tumour antigen and its loading, a wide range of adjuvants and different modes of vaccine delivery. Key insights from pre-clinical studies, and lessons learned from early clinical testing drive progress towards improved vaccines. The potential to fortify responses with other modalities of immunotherapy makes clinically effective "second generation" DC vaccination strategies a priority for cancer immune therapists.

Echinacea pupurea extracts promote murine dendritic cell maturation by activation of JNK, p38 MAPK and NF-κB pathways

Dendritic cells (DCs) comprise a system of highly professional antigen presenting cells (APCs) which connect innate and adaptive immunity by undergoing dramatic shift in their maturation state. Phytomedicine Echinacea purpurea extracts (EE) could modulate murine dendritic cell fate and function. However, the underlying mechanism of EE on DCs development and maturation remains limited. In this study, immature DCs were induced phenotypic maturation with up-regulated expression of key accessory molecules and the phagocytic activity was decreased after being treated with EE (400 μg/ml) for 48 h. We found that TLR1/2, JNK, p38-MAPK and NF-κB pathways were activated following EE exposure. Notably, JNK activation was demonstrated to be associated with increased IFN-γ response while p38-MAPK pathway exhibited immuno-regulatory effects via induction of IL-10 and TGF-β1. Furthermore, it was verified that NF-κB signaling was responsible for EE-induced synthesis of IFN-γ, IL-12 and TGF-β1, but not for IL-10 induction. These results indicate that EE have the immunomodulatory potency to promote both phenotypic and functional maturation of BMDCs via modulating the activation of JNK, p38-MAPK and NF-κB pathways. Our findings contributed to the current understanding of the immunoregulatory function of EE and the mechanism of DCs maturation.

Overcoming Oncogenic Mediated Tumor Immunity in Prostate Cancer

Immunotherapy is being tested intensively in clinical trials for prostate cancer; it includes immune checkpoint inhibition, prostate specific antigen (PSA) vaccines and dendritic cell-based strategies. Despite increasing evidence for clinical responses, the consensus of multiple trials is that prostate cancers are poorly responsive to immunotherapy. Prostate cancer has a high degree of pathological and genetic heterogeneity compared to other cancer types, which may account for immunotherapeutic resistance. This hypothesis also implies that select types of prostate tumors may be differentially responsive to immune-based strategies and that the clinical stage, pathological grade and underlying genetic landscape may be important criteria in identifying tumors that respond to immune therapies. One strategy is to target oncogenic driver pathways in combination with immunotherapies with the goal of overcoming tumor immunity and broadening the number of patients achieving a clinical response. In this analysis, we address the hypothesis that driver oncogenic signaling pathways regulate cancer progression, tumor immunity and resistance to current immune therapeutics in prostate cancer. We propose that increased responsiveness may be achieved through the combined use of immunotherapies and inhibitors targeting tumor cell autonomous pathways that contribute towards anti-tumor immunity in patients with prostate cancer.

Novel B7-H4-mediated crosstalk between human non-Hodgkin lymphoma cells and tumor-associated macrophages leads to immune evasion via secretion of IL-6 and IL-10

Non-Hodgkin lymphoma (NHL) is an incurable lymphoproliferative cancer, and patients with NHL have a poor prognosis. The present study explored the regulatory mechanism of expression and possible roles of the immunosuppressive B7-H4 molecule in human NHL. For functional studies, NHL-reactive T cell lines were generated via the isolation of allogeneic CD3+ T cells from healthy donors and repeated in vitro stimulation with irradiated NHL cells isolated from patients. B7-H4 was found to be distributed in NHL cells and tissues, and its surface protein expression levels were further upregulated by the incubation of NHL cells with interleukin (IL)-6, IL-10, or interferon-γ. Additionally, the supernatants of tumor-associated macrophages (tMφs) upregulated B7-H4 surface expression by producing IL-6 and IL-10. B7-H4 expressed in NHL cells inhibited the cytotoxic activity of NHL-reactive T cells. Conversely, the inhibition of B7-H4 in NHL cells promoted T cell immunity and sensitized NHL cells to cytolysis. Furthermore, tMφs induced B7-H4 promoted NHL cell evasion of the T cell immune response. In conclusion, this study shows that NHL-expressed B7-H4 is an important immunosuppressive factor that inhibits host anti-tumor immunity to NHL. Targeting tumor-expressed B7-H4 may thus provide a new treatment strategy for NHL patients.

Extracellular matrix and the myeloid-in-myeloma compartment: balancing tolerogenic and immunogenic inflammation in the myeloma niche

The last 10-15 years have witnessed a revolution in treating multiple myeloma, an incurable cancer of Ab-producing plasma cells. Advances in myeloma therapy were ushered in by novel agents that remodel the myeloma immune microenvironment. The first generation of novel agents included immunomodulatory drugs (thalidomide analogs) and proteasome inhibitors that target crucial pathways that regulate immunity and inflammation, such as NF-κB. This paradigm continued with the recent regulatory approval of mAbs (elotuzumab, daratumumab) that impact both tumor cells and associated immune cells. Moreover, recent clinical data support checkpoint inhibition immunotherapy in myeloma. With the success of these agents has come the growing realization that the myeloid infiltrate in myeloma lesions-what we collectively call the myeloid-in-myeloma compartment-variably sustains or deters tumor cells by shaping the inflammatory milieu of the myeloma niche and by promoting or antagonizing immune-modulating therapies. The myeloid-in-myeloma compartment includes myeloma-associated macrophages and granulocytes, dendritic cells, and myeloid-derived-suppressor cells. These cell types reflect variable states of differentiation and activation of tumor-infiltrating cells derived from resident myeloid progenitors in the bone marrow-the canonical myeloma niche-or myeloid cells that seed both canonical and extramedullary, noncanonical niches. Myeloma-infiltrating myeloid cells engage in crosstalk with extracellular matrix components, stromal cells, and tumor cells. This complex regulation determines the composition, activation state, and maturation of the myeloid-in-myeloma compartment as well as the balance between immunogenic and tolerogenic inflammation in the niche. Redressing this balance may be a crucial determinant for the success of antimyeloma immunotherapies.

Efficacy of host-dendritic cell vaccinations with or without minor histocompatibility antigen loading, combined with donor lymphocyte infusion in multiple myeloma patients

Donor lymphocyte infusions (DLI) can induce durable remissions in multiple myeloma (MM) patients, but this occurs rather infrequently. As the graft-versus-tumor (GvT) effect of DLI depends on the presence of host-dendritic cells (DCs), we tested in a phase I/II trial whether the efficacy of DLI could be improved by simultaneous vaccination with host-DCs. We also analyzed the possibility of further improving the GvT effect by loading the DCs with peptides of mismatched hematopoietic cell-specific minor histocompatibility antigens (mHags). Fifteen MM patients not responding to a first DLI were included. Eleven patients could be treated with a second equivalent dose DLI combined with DC vaccinations, generated from host monocytes (moDC). For four patients, the DC products did not meet the quality criteria. In four of the treated patients the DCs were loaded with host mHag peptides. Toxicity was limited and no acute GvHD occurred. Most patients developed objective anti-host T-cell responses and in one patient a distinct mHag-specific T-cell response accompanied a temporary clinical response. These findings confirm that DLI combined with host-DC vaccination, either unloaded or loaded with mHag peptides, is feasible, safe and capable of inducing host-specific T-cell responses. The limited clinical effects may be improved by developing more immunogenic DC products or by combining this therapy with immune potentiating modalities like checkpoint inhibitors.

Dysregulation of TGFβ1 Activity in Cancer and Its Influence on the Quality of Anti-Tumor Immunity

TGFβ1 is a pleiotropic cytokine that exhibits a variety of physiologic and immune regulatory functions. Although its influence on multiple cell types is critical for the regulation of numerous biologic processes in the host, dysregulation of both TGFβ1 expression and activity is frequently observed in cancer and contributes to various aspects of cancer progression. This review focuses on TGFβ1’s contribution to tumor immune suppression and escape, with emphasis on the influence of this regulatory cytokine on the differentiation and function of dendritic cells and T cells. Clinical trials targeting TGFβ1 in cancer patients are also reviewed, and strategies for future therapeutic interventions that build on our current understanding of immune regulation by TGFβ1 are discussed.

Human breast cancer-derived soluble factors facilitate CCL19-induced chemotaxis of human dendritic cells

Breast cancer remains as a challenging disease with high mortality in women. Increasing evidence points the importance of understanding a crosstalk between breast cancers and immune cells, but little is known about the effect of breast cancer-derived factors on the migratory properties of dendritic cells (DCs) and their consequent capability in inducing T cell immune responses. Utilizing a unique 3D microfluidic device, we here showed that breast cancers (MCF-7, MDA-MB-231, MDA-MB-436 and SK-BR-3)-derived soluble factors increase the migration of DCs toward CCL19. The enhanced migration of DCs was mainly mediated via the highly activated JNK/c-Jun signaling pathway, increasing their directional persistence, while the velocity of DCs was not influenced, particularly when they were co-cultured with triple negative breast cancer cells (TNBCs or MDA-MB-231 and MDA-MB-436). The DCs up-regulated inflammatory cytokines IL-1β and IL-6 and induced T cells more proliferative and resistant against activation-induced cell death (AICD), which secret high levels of inflammatory cytokines IL-1β, IL-6 and IFN-γ. This study demonstrated new possible evasion strategy of TNBCs utilizing their soluble factors that exploit the directionality of DCs toward chemokine responses, leading to the building of inflammatory milieu which may support their own growth.

Maytansinoid immunoconjugate IMGN901 is cytotoxic in a three-dimensional culture model of multiple myeloma

Environmental-mediated drug-resistance (EM-DR) presents a major challenge for therapeutic development. Tissue microenvironment in the form of extracellular matrix, soluble factors, and stroma contribute to EM-DR. In multiple myeloma (MM), drug-resistance has hindered treatment success with 5-year survival rates remaining <50%. Here we evaluated IMGN901, a maytansinoid immunoconjugate, for its ability to overcome EM-DR alone or in combination with lenalidomide or dexamethasone. We show that while adhesion of MM cells to the extracellular matrix reduces potency of IMGN901, it remains cytotoxic with an average LC50=43 nM. However, only a combination of IMGN901, lenalidomide, and dexamethasone was able to overcome drug-resistance arising from the direct contact between MM and stromal cells. We demonstrate that multi-drug resistance protein-1 (MDR-1) was upregulated in MM cells grown in contact with stroma, likely responsible for the observed resistance. This study emphasizes the importance of incorporating the elements of tumor microenvironment during preclinical testing of novel therapeutics.

High glucose and hyperglycemic sera from type 2 diabetic patients impair DC differentiation by inducing ROS and activating Wnt/β-catenin and p38 MAPK

Type 2 is the type of diabetes with higher prevalence in contemporary time, representing about 90% of the global cases of diabetes. In the course of diabetes, several complications can occur, mostly due to hyperglycemia and increased reactive oxygen species (ROS) production. One of them is represented by an increased susceptibility to microbial infections and by a reduced capacity to clear them. Therefore, knowing the impact of hyperglycemia on immune system functionality is of utmost importance for the management of the disease. In this study, we show that medium containing high glucose reduced the in-vitro differentiation of monocytes into functional DCs and their activation mediated by PAMPs or DAMPs. Most importantly, the same effects were mediated by the hyperglycemic sera derived by type 2 diabetic patients, mimicking a more physiologic condition. DC dysfunction caused by hyperglycemia may be involved in the inefficient control of infections observed in diabetic patients, given the pivotal role of these cells in both the innate and adaptive immune response. Searching for the molecular mechanisms underlying DC dysfunction, we found that canonical Wnt/β-catenin and p38 MAPK pathways were activated in the DCs differentiated either in the presence of high glucose or of hyper-glycemic sera. Interestingly, the activation of these pathways and the DC immune dysfunction were partially counteracted by the anti-oxidant quercetin, a flavonoid already known to exert several beneficial effects in diabetes.

Disruptive environmental chemicals and cellular mechanisms that confer resistance to cell death

Cell death is a process of dying within biological cells that are ceasing to function. This process is essential in regulating organism development, tissue homeostasis, and to eliminate cells in the body that are irreparably damaged. In general, dysfunction in normal cellular death is tightly linked to cancer progression. Specifically, the up-regulation of pro-survival factors, including oncogenic factors and antiapoptotic signaling pathways, and the down-regulation of pro-apoptotic factors, including tumor suppressive factors, confers resistance to cell death in tumor cells, which supports the emergence of a fully immortalized cellular phenotype. This review considers the potential relevance of ubiquitous environmental chemical exposures that have been shown to disrupt key pathways and mechanisms associated with this sort of dysfunction. Specifically, bisphenol A, chlorothalonil, dibutyl phthalate, dichlorvos, lindane, linuron, methoxychlor and oxyfluorfen are discussed as prototypical chemical disruptors; as their effects relate to resistance to cell death, as constituents within environmental mixtures and as potential contributors to environmental carcinogenesis.

MicroRNA-22 impairs anti-tumor ability of dendritic cells by targeting p38

Dendritic cells (DCs) play a critical role in triggering anti-tumor immune responses. Their intracellular p38 signaling is of great importance in controlling DC activity. In this study, we identified microRNA-22 (miR-22) as a microRNA inhibiting p38 protein expression by directly binding to the 3' untranslated region (3'UTR) of its mRNA. The p38 down-regulation further interfered with the synthesis of DC-derived IL-6 and the differentiation of DC-driven Th17 cells. Moreover, overexpression of miR-22 in DCs impaired their tumor-suppressing ability while miR-22 inhibitor could reverse this phenomenon and improve the curative effect of DC-based immunotherapy. Thus, our results highlight a suppressive role for miR-22 in the process of DC-invoked anti-tumor immunity and that blocking this microRNA provides a new strategy for generating potent DC vaccines for patients with cancer.

Tumor cell p38 MAPK: A trigger of cancer bone osteolysis

Osteolytic bone destruction is a hallmark of bone-metastatic cancers. Current therapy is unable to completely cure or prevent this disease in patients. The p38 mitogen-activated protein kinase (MAPK) affects a diverse range of intracellular responses with well-known roles in development, cell-cycle and differentiation, inflammation, apoptosis, senescence, and tumorigenesis. This article is an overview of the contribution of tumor cell-expressed p38 MAPK to the regulation of osteoclastogenesis, osteoblastogenesis, and osteolyticbone lesions.

Treatment with lenalidomide induces immunoactivating and counter-regulatory immunosuppressive changes in myeloma patients

Lenalidomide activates the immune system, but the exact immunomodulatory mechanisms of lenalidomide in vivo are poorly defined. In an observational study we assessed the impact of lenalidomide on different populations of immune cells in multiple myeloma patients. Lenalidomide therapy was associated with increased amounts of a CD8(+) T cell subset, phenotypically staged between classical central memory T cells (TCM) and effector memory T cells (TEM), consequently termed TCM/TEM. The moderate expression of perforin/granzyme and phenotypical profile of these cells identifies them as not yet terminally differentiated, which makes them promising candidates for the anti-tumour response. In addition, lenalidomide-treated patients showed higher abundance of CD14(+) myeloid cells co-expressing CD15. This population was able to inhibit both CD4(+) and CD8(+) T cell proliferation in vitro and could thus be defined as a so far undescribed novel myeloid-derived suppressor cell (MDSC) subtype. We observed a striking correlation between levels of TCM/TEM, mature regulatory T cells (T(regs)) and CD14(+) CD15(+) MDSCs. In summary, lenalidomide induces both activating and inhibitory components of the immune system, indicating the existence of potential counter-regulatory mechanisms. These findings provide new insights into the immunomodulatory action of lenalidomide.

Toll-like receptor 4 prompts human breast cancer cells invasiveness via lipopolysaccharide stimulation and is overexpressed in patients with lymph node metastasis

Toll-like receptor (TLR)4-mediated signaling has been implicated in tumor cell invasion, survival, and metastasis in a variety of cancers. This study investigated the expression and biological role of TLR4 in human breast cancer metastasis. MCF-7 and MDA-MB-231 are human breast cancer cell lines with low and high metastatic potential, respectively. Using lipopolysaccharide (LPS) to stimulate MCF-7 and MDA-MB-231 cells, expression of TLR4 mRNA and protein increased compared with that in control cells. TLR4 activation notably up-regulated expression of matrix metalloproteinase (MMP)-2, MMP-9 and vascular endothelial growth factor(VEGF) mRNA and their secretion in the supernatants of both cell lines. LPS enhanced invasion of MDA-MB-231 cells by transwell assay and MCF-7 cells by wound healing assay. LPS triggered increased expression of TLR4 downstream signaling pathway protein myeloid differentiation factor 88(MyD88) and resulted in interleukin (IL)-6 and IL-10 higher production by human breast cancer cells. Stimulation of TLR4 with LPS promoted tumorigenesis and formed metastatic lesions in liver of nude mice. Moreover, expression of TLR4 and MyD88 as well as invasiveness and migration of the cells could be blocked by TLR4 antagonist. Combined with clinicopathological parameters, TLR4 was overexpressed in human breast cancer tissue and correlated with lymph node metastasis. These findings indicated that TLR4 may participate in the progression and metastasis of human breast cancer and provide a new therapeutic target.

Cellular immunotherapy in multiple myeloma: lessons from preclinical models

The majority of multiple myeloma patients relapse with the current treatment strategies, raising the need for alternative therapeutic approaches. Cellular immunotherapy is a rapidly evolving field and currently being translated into clinical trials with encouraging results in several cancer types, including multiple myeloma. Murine multiple myeloma models are of critical importance for the development and refinement of cellular immunotherapy. In this review, we summarize the immune cell changes that occur in multiple myeloma patients and we discuss the cell-based immunotherapies that have been tested in multiple myeloma, with a focus on murine models.

p38 MAPK-inhibited dendritic cells induce superior antitumour immune responses and overcome regulatory T-cell-mediated immunosuppression

Dendritic cell (DC)-based cancer immunotherapy is a promising method, but so far has demonstrated limited clinical benefits. Regulatory T cells (Tregs) represent a major obstacle to cancer immunotherapy approaches. Here we show that inhibiting p38 MAPK during DC differentiation enables DCs to activate tumour-specific effector T cells (Teff), inhibiting the conversion of Treg and compromising Treg inhibitory effects on Teff. Inhibition of p38 MAPK in DCs lowers expression of PPARγ, activating p50 and upregulating OX40L expression in DCs. OX40L/OX40 interactions between DCs and Teff and/or Treg are critical for priming effective and therapeutic antitumour responses. Similarly, p38 MAPK inhibition also augments the T-cell stimulatory capacity of human monocyte-derived DCs in the presence of Treg. These findings contribute to ongoing efforts to improve DC-based immunotherapy in human cancers.

Future agents and treatment directions in multiple myeloma

The development of bortezomib and immunomodulatory agents resulted in a revolution in the treatment of multiple myeloma (MM). Moreover, second-generation proteasome inhibitors (carfilzomib) and immunomodulatory agents (pomalidomide) have recently been approved. Nevertheless, the incurability of this disease requires other drugs with different mechanisms of action to either prolong the survival of patients refractory to current therapies, or achieve cure. Active research has been done exploring the pathogenesis of MM and searching for novel, druggable targets. In this regard, some of these novel agents seem promising, such as monoclonal antibodies (anti-CD38 - daratumumab or anti-CS1 - elotuzumab) or the kinesin protein inhibitor Arry-520. Other agents under investigation are kinase inhibitors, signaling pathways inhibitors or deacetylase inhibitors. With so many novel agents under investigation, future therapy in MM will probably involve the combined use of the already approved drugs with some of those newly discovered.

An array of possibilities in cancer research using cytokine antibody arrays

Protein arrays have shown potential applications in cancer research. After several decades of research, it has become evident that many cytokines are central to the development of cancer and its treatment. Cytokine antibody arrays that have been designed to simultaneously detect multiple cytokines are not only available, but show a diversity of applications in the study of many diseases in addition to cancer. This review will focus on the implementation of cytokine antibody arrays in many aspects of cancer research, such as biomarker discovery, molecular mechanisms of cancer development, preclinical studies and the effects of cancer compounds.

Characterization of LY2228820 dimesylate, a potent and selective inhibitor of p38 MAPK with antitumor activity

p38α mitogen-activated protein kinase (MAPK) is activated in cancer cells in response to environmental factors, oncogenic stress, radiation, and chemotherapy. p38α MAPK phosphorylates a number of substrates, including MAPKAP-K2 (MK2), and regulates the production of cytokines in the tumor microenvironment, such as TNF-α, interleukin-1β (IL-1β), IL-6, and CXCL8 (IL-8). p38α MAPK is highly expressed in human cancers and may play a role in tumor growth, invasion, metastasis, and drug resistance. LY2228820 dimesylate (hereafter LY2228820), a trisubstituted imidazole derivative, is a potent and selective, ATP-competitive inhibitor of the α- and β-isoforms of p38 MAPK in vitro (IC(50) = 5.3 and 3.2 nmol/L, respectively). In cell-based assays, LY2228820 potently and selectively inhibited phosphorylation of MK2 (Thr334) in anisomycin-stimulated HeLa cells (at 9.8 nmol/L by Western blot analysis) and anisomycin-induced mouse RAW264.7 macrophages (IC(50) = 35.3 nmol/L) with no changes in phosphorylation of p38α MAPK, JNK, ERK1/2, c-Jun, ATF2, or c-Myc ≤ 10 μmol/L. LY2228820 also reduced TNF-α secretion by lipopolysaccharide/IFN-γ-stimulated macrophages (IC(50) = 6.3 nmol/L). In mice transplanted with B16-F10 melanoma, tumor phospho-MK2 (p-MK2) was inhibited by LY2228820 in a dose-dependent manner [threshold effective dose (TED)(70) = 11.2 mg/kg]. Significant target inhibition (>40% reduction in p-MK2) was maintained for 4 to 8 hours following a single 10 mg/kg oral dose. LY2228820 produced significant tumor growth delay in multiple in vivo cancer models (melanoma, non-small cell lung cancer, ovarian, glioma, myeloma, breast). In summary, LY2228820 is a p38 MAPK inhibitor, which has been optimized for potency, selectivity, drug-like properties (such as oral bioavailability), and efficacy in animal models of human cancer.

Pathological mobilization and activities of dendritic cells in tumor-bearing hosts: challenges and opportunities for immunotherapy of cancer

A common characteristic of solid tumors is the pathological recruitment of immunosuppressive myeloid cells, which in certain tumors includes dendritic cells (DCs). DCs are of particular interest in the field of cancer immunotherapy because they induce potent and highly specific anti-tumor immune responses, particularly in the early phase of tumorigenesis. However, as tumors progress, these cells can be transformed into regulatory cells that contribute to an immunosuppressive microenvironment favoring tumor growth. Therefore, controlling DC phenotype has the potential to elicit effective anti-tumor responses while simultaneously weakening the tumor’s ability to protect itself from immune attack. This review focuses on the dual nature of DCs in the tumor microenvironment, the regulation of DC phenotype, and the prospect of modifying DCs in situ as a novel immunotherapeutic approach.

CD137 stimulation and p38 MAPK inhibition improve reactivity in an in vitro model of glioblastoma immunotherapy

Dendritic cell vaccination has become an interesting option for cancer immunotherapy. Tumor-lysate-pulsed dendritic cells (DC) can prime naïve T cells and induce the regression of established tumors including gliomas as shown in various animal models. Despite hopeful results even in clinical studies, the outcome for many patients is still unsatisfying. In the present study, we tested the combination of tumor-lysate-pulsed dendritic cells (TPDC) with a monoclonal antibody against CD137, a monoclonal antibody against CD25 (daclizumab) and a specific p38 mitogen-activated protein kinase (p38 MAPK) inhibitor (SB203580) for improving immunostimulation in an in vitro model of immunotherapy for human gliomas. We observed a higher secretion of interferon gamma by TPDC-primed peripheral blood mononuclear cells (PBMC) that were incubated with an antibody against CD137 or the p38 MAPK inhibitor. In addition, we observed higher specific lysis of tumor cells after incubation of PBMC with the p38 MAPK inhibitor or the anti-CD137 antibody. In contrast, incubation of TPDC-primed PBMC with the anti-CD25 antibody did enhance neither interferon gamma secretion nor cellular cytotoxicity. Cell depletion experiments demonstrated that the immune reaction induced by TPDC is strongly dependent on CD4-positive and CD8-positive cells. Incubation of DC during maturation and antigen loading with the anti-CD137 antibody did not enhance cytotoxicity and interferon gamma secretion in comparison with application of the anti-CD137 antibody during priming. In conclusion, our data suggest that p38 MAPK inhibition and anti-CD137 antibodies can enhance the immune response against glioblastoma cells.

Tumor-altered dendritic cell function: implications for anti-tumor immunity

Dendritic cells (DC) are key regulators of both innate and adaptive immunity, and the array of immunoregulatory functions exhibited by these cells is dictated by their differentiation, maturation, and activation status. Although a major role for these cells in the induction of immunity to pathogens has long been appreciated, data accumulated over the last several years has demonstrated that DC are also critical regulators of anti-tumor immune responses. However, despite the potential for stimulation of robust anti-tumor immunity by DC, tumor-altered DC function has been observed in many cancer patients and tumor-bearing animals and is often associated with tumor immune escape. Such dysfunction has significant implications for both the induction of natural anti-tumor immune responses as well as the efficacy of immunotherapeutic strategies that target endogenous DC in situ or that employ exogenous DC as part of anti-cancer immunization maneuvers. In this review, the major types of tumor-altered DC function will be described, with emphasis on recent insights into the mechanistic bases for the inhibition of DC differentiation from hematopoietic precursors, the altered programing of DC precursors to differentiate into myeloid-derived suppressor cells or tumor-associated macrophages, the suppression of DC maturation and activation, and the induction of immunoregulatory DC by tumors, tumor-derived factors, and tumor-associated cells within the milieu of the tumor microenvironment. The impact of these tumor-altered cells on the quality of the overall anti-tumor immune response will also be discussed. Finally, this review will also highlight questions concerning tumor-altered DC function that remain unanswered, and it will address factors that have limited advances in the study of this phenomenon in order to focus future research efforts in the field on identifying strategies for interfering with tumor-associated DC dysfunction and improving DC-mediated anti-tumor immunity.

Cellular mechanisms of multiple myeloma bone disease

Multiple myeloma (MM) is a hematologic malignancy of differentiated plasma cells that accumulates and proliferates in the bone marrow. MM patients often develop bone disease that results in severe bone pain, osteolytic lesions, and pathologic fractures. These skeletal complications have not only a negative impact on quality of life but also a possible effect in overall survival. MM osteolytic bone lesions arise from the altered bone remodeling due to both increased osteoclast activation and decreased osteoblast differentiation. A dysregulated production of numerous cytokines that can contribute to the uncoupling of bone cell activity is well documented in the bone marrow microenvironment of MM patients. These molecules are produced not only by malignant plasma cells, that directly contribute to MM bone disease, but also by bone, immune, and stromal cells interacting with each other in the bone microenvironment. This review focuses on the current knowledge of MM bone disease biology, with particular regard on the role of bone and immune cells in producing cytokines critical for malignant plasma cell proliferation as well as in osteolysis development. Therefore, the understanding of MM pathogenesis could be useful to the discovery of novel agents that will be able to both restore bone remodelling and reduce tumor burden.

Regulating the regulators in cancer-immunosuppression in multiple myeloma (MM)

An effective immune response requires a prompt but measured action against the pathological insult, to prevent over-zealous inflammatory-mediated tissue destruction. In cancer, defective or incompetent immune responses may paradoxically result in disease progression despite an immune attempt at elimination. Tumour-induced immunosuppression may not only result from soluble factors and altered antigenicity, but also from cellular-mediated tumour-induced immune evasion. Multiple myeloma (MM) is associated with both cellular and humoral immune deficiencies and increased T(Reg) cells. In vitro modelling has indicated that the tumour cells directly induce functional T(Reg) cells. In light of this recent evidence, it now seems that the most promising and synergistic approaches for cancer immunotherapy would involve specific anti-tumour immunity and simultaneous reduction of tumour-induced immune-regulation. This review sets out the basic understanding of the human immune response, its dysregulation in cancer and proposes how this knowledge may influence future treatment strategies to maximise the anti-tumour immune response.

Immune evasion of mantle cell lymphoma: expression of B7-H1 leads to inhibited T-cell response to and killing of tumor cells

Clinical trials of immunotherapy in mantle cell lymphoma have not yet delivered desirable results, partly because of the inhibitory machinery of the tumor and its microenvironment. Here we investigated the role of B7-H1, a member of the B7 family of co-stimulatory/co-inhibitory ligands, in mantle cell lymphoma-mediated immunosuppression. Allogeneic CD3(+), CD4(+) and CD8(+) T cells were purified and co-cultured with irradiated mantle cell lymphoma cells. Mantle cell lymphoma-reactive T-cell lines from HLA-A*0201(+) healthy blood donors were generated after in vitro restimulation, and were subjected to functional tests. We found that B7-H1 expressed on mantle cell lymphoma cells was able to inhibit T-cell proliferation induced by the tumor cells, impair the generation of antigen-specific T-cell responses, and render mantle cell lymphoma cells resistant to T-cell-mediated cytolysis. Blocking or knocking down B7-H1 on mantle cell lymphoma cells enhanced T-cell responses and restored tumor-cell sensitivity to T-cell-mediated killing in vitro and in vivo. Knocking down B7-H1 on mantle cell lymphoma cells primed more CD4(+) or CD8(+) memory effector T cells. Our study demonstrates for the first time that lymphoma cell-expressed B7-H1 may lead to the suppression of host anti-tumor immune responses in mantle cell lymphoma and targeting tumor cell B7-H1 may represent a novel approach to improve the efficacy of immunotherapy in patients with mantle cell lymphoma.

MGN-3 arabinoxylan rice bran modulates innate immunity in multiple myeloma patients

Dendritic cells (DCs) and natural killer (NK) cells are central components of innate immunity for controlling tumor growth. The therapeutic effects of certain anti-myeloma drugs are partially mediated by targeting the innate immune response. In addition, novel types of natural compounds have been developed that efficiently modulate the activity of both the cellular and humoral compartments of immunity. MGN-3 is known as an activator of natural killer cells, inducer of apoptosis and cytokine production, and modulator of dendritic cell maturation and differentiation in vitro. We have performed a randomized, placebo-controlled study to examine the effects of MGN-3 on innate immune system parameters in 48 multiple myeloma patients. We performed immunophenotypic analysis of peripheral blood samples, determined NK cell activity, and assessed the cytokine profiles of plasma before and during 3 months of treatment. The results demonstrate a clear increase in NK activity in MGN-3-treated patients compared to the placebo group, an increased level of myeloid DCs in peripheral blood, and augmented concentrations of T helper cell type 1-related cytokines. The present study suggests that MGN-3 may represent an immunologically relevant product for activating innate immunity in multiple myeloma patients and warrants further testing to demonstrate clinical efficacy.

Immune dysfunction in multiple myeloma

SUMMARY Although there have been advances in the field, multiple myeloma, the second most common hematological malignancy, remains an incurable disease characterized by ever-shortening cycles of treatment and relapse. Myriad experimental and observational studies over the last few decades have comprehensively documented a state of profound immune dysfunction, which is progressive and correlated with disease stage. Nonetheless, immune responses against the tumor have demonstrated efficacy ex vivo, in animal models and in human disease. In this review we examine the immune defects in multiple myeloma and consider current and future approaches toward correction and manipulation of immune responses to affect clinically useful antitumor effects.

p38 MAPK in myeloma cells regulates osteoclast and osteoblast activity and induces bone destruction

p38 mitogen-activated protein kinase (MAPK), which is constitutively activated in human myeloma, has been implicated in bone destruction by this cancer, but the processes it recruits are obscure. In this study, we show that p38 activity in myeloma inhibits osteoblast differentiation and bone formation, but also enhances osteoclast maturation and bone resorption. p38 regulated the expression and secretion of the Wnt pathway antagonist DKK-1 and the monocyte chemoattractant MCP-1. Attenuating p38, DKK-1, or MCP-1 were each sufficient to reduce bone lesions in vivo. Although it is well known that DKK-1 inhibits osteoblast differentiation, we found that together with MCP-1, it could also promote osteoclast differentiation and bone resorption. The latter effects were mediated by enhancing expression of RANK in osteoclast progenitor cells and by upregulating secretion of its ligand RANKL from stromal cells and mature osteoblasts. In summary, our study defined the mechanisms by which p38 signaling in myeloma cells regulates osteoblastogenesis, osteoclastogenesis, and bone destruction. Our findings, which may have implications for bone invasion by other cancers where p38 is elevated, strongly suggests that targeting p38 for inhibition may offer an effective therapeutic approach to treat osteolytic bone lesions in patients with myeloma.

Immunotherapy of cancer in 2012

The immunotherapy of cancer has made significant strides in the past few years due to improved understanding of the underlying principles of tumor biology and immunology. These principles have been critical in the development of immunotherapy in the laboratory and in the implementation of immunotherapy in the clinic. This improved understanding of immunotherapy, enhanced by increased insights into the mechanism of tumor immune response and its evasion by tumors, now permits manipulation of this interaction and elucidates the therapeutic role of immunity in cancer. Also important, this improved understanding of immunotherapy and the mechanisms underlying immunity in cancer has fueled an expanding array of new therapeutic agents for a variety of cancers. Pegylated interferon-α2b as an adjuvant therapy and ipilimumab as therapy for advanced disease, both of which were approved by the United States Food and Drug Administration for melanoma in March 2011, are 2 prime examples of how an increased understanding of the principles of tumor biology and immunology have been translated successfully from the laboratory to the clinical setting. Principles that guide the development and application of immunotherapy include antibodies, cytokines, vaccines, and cellular therapies. The identification and further elucidation of the role of immunotherapy in different tumor types, and the development of strategies for combining immunotherapy with cytotoxic and molecularly targeted agents for future multimodal therapy for cancer will enable even greater progress and ultimately lead to improved outcomes for patients receiving cancer immunotherapy.

Toll-like receptor-4 signaling in mantle cell lymphoma: effects on tumor growth and immune evasion

BACKGROUND

Mantle cell lymphoma (MCL) is an incurable B-cell malignancy, and patients with this disease have the poorest prognosis among all patients with B-cell lymphomas. The signaling pathways that trigger MCL escape from immune surveillance are unclear. Because Toll-like receptors (TLRs) initiate innate and adaptive immune responses against invading pathogens, the authors investigated the impact of TLR signaling in MCL cells.

METHODS

TLR expression was examined in MCL cell lines and in primary tumors. The examination focused on TLR4 and its ligand lipopolysaccharide (LPS) on MCL cells and their function on MCL proliferation and immune evasion.

RESULTS

MCL cells expressed multiple TLRs, and TLR4 was among the highest expressed molecules. The activation of TLR4 signaling in MCL cells by LPS induced MCL proliferation and up-regulated the secretion of cytokines like interleukin-6 (IL-6), IL-10, and vascular endothelial growth factor (VEGF). LPS-pretreated MCL cells inhibited the proliferation and cytolytic activity of T cells by secreted IL-10 and VEGF, and neutralizing antibodies against these cytokines restored their functions. Similar results were observed in TLR4-positive/myeloid differentiation 88 (MyD88)-positive primary lymphoma cells but not in TLR4-positive/MyD88-negative primary lymphoma cells from patients with MCL. Knockdown of TLR4 on MCL cells abrogated the effect of LPS on MCL cells in term of cell growth or secretion of the cytokines and evasion of the immune system.

CONCLUSIONS

The current results indicated that TLR4 signaling triggers a cascade that leads to MCL growth and evasion from immune surveillance. Thus, TLR4 signaling molecules may be novel therapeutic targets in patients with MCL.

IL-10 production in non-small cell lung carcinoma patients is regulated by ERK, P38 and COX-2

Immune dysfunction is hallmark of patients with non–small cell lung carcinoma (NSCLC). The molecular mechanism involved in COX-2– and PGE2-mediated production of immunosuppressive cytokine IL-10 is not well-understood. Our study addresses the involvement of T cell downstream signalling intermediates, cytokines (IL-10 and IFN-γ) and their transcription factors (T-bet and GATA-3) in COX-2–mediated regulation of lymphocyte functions in NSCLC patients. In comparison to healthy individual, a marked decrease in lymphocyte proliferation to anti-CD3 MAb was observed in NSCLC patients by thymidine incorporation assay. Using flow cytometry, decrease in intracellular calcium release with increase in reactive oxygen species was observed in lymphocytes of NSCLC patients. These patients showed increased IL-10 and PGE2 with reduced IFN-γ production by ELISA. Results demonstrated defect in regulation of transcription factors T-bet and GATA-3 as analysed by Western blotting (WB), immunoprecipitation and EMSA. Overexpression of p-p38, p-ERK and COX-2 were observed with diminished p-JNK by WB. IL-10/IFN-γ levels were found to be differentially regulated via p38 and ERK mitogen-activated protein kinase (MAPK) pathways in cooperation with COX-2. Inhibition of these pathways using selective inhibitors lead to increased lymphocyte proliferative response to anti-CD3 MAb and IFN-γ production with decrease in IL-10 production. Studies showed involvement of ERK, p38 and COX-2 pathways in high IL-10 production, driven by lung tumour derived PGE2. The selective COX-2 inhibitor rofecoxib showed ability to alter the cytokine balance by affecting regulation of T-bet and GATA-3 transcription factors.